The Lemon Beach House (海の家れもん, Umi no ya Remon) also commonly referred to as the Lemon or simply Lemon is the place where it all began. This is where Ika made her first appearance, declaring it as her base of operation due to it being the closest to the beach.

Where the Lemon beach house stands.

The Lemon serves as the main setting for the Shinryaku! Ika Musume story (for both manga and anime - despite the fact that Aizawas' place is also used more often in the manga).

Initially Ika spent her days after trying to invade living at the Lemon. However, after the TV broke, Chizuru invited her to spend a night at Aizawas' place. That one night continues infinitely as the Aizawas begin to accept Ika as part of family.

All the staff members (excluding Ika Musume ) wear the same uniform. The uniform differs between the manga and anime version, though they still share similar qualities.

Both uniforms share a yellow t-shirt and black shorts, In the anime the Lemon uniform has a very simplistic design, almost entirely bland save for a small lemon on the left side, above the chest.
In the manga the uniform is adorned with 海の家 れもん (Beach House Lemon) wordings. Both outfits also involve wearing socks, and wearing tan/white sneakers.